1. Technical Field
The present invention relates to a loudspeaker used for a portable telephone and other various electronic apparatuses, and to electronic apparatuses using the loudspeaker.
2. Background Art
In various electronic apparatuses such as mobile communication apparatuses represented by a portable telephone, improvement in performance and functions is demanded. In addition, for the purpose of improving convenience such as portability, electronic apparatuses are required to be smaller, more lightweight, and more compact.
In such a background, it is becoming essential for also loudspeakers and receivers mounted in various electronic apparatuses to have an improved space factor and to be smaller, more lightweight, and more compact, while high performance and low cost are maintained.
A conventional loudspeaker is described with reference to FIG. 13. FIG. 13 is a perspective view of magnetic circuit 24 of a conventional loudspeaker. Magnetic circuit 24 includes bottom plate 23, and a plurality of magnets 22A, 22B, and 22C coupled to bottom plate 23, and top plates 21A, 21B, and 21C coupled to magnets 22A, 22B, and 22C, respectively, at the opposite side to bottom plate 23.
Herein, a magnetic gap includes linearly extending magnetic gaps 25A and 25B. A voice coil wound in a track shape or a rectangular shape, is inserted into magnetic gaps 25A and 25B. A magnetization direction of magnets 22A and 22B disposed at the outer side of the voice coil and a magnetization direction of magnet 22C disposed at the inner side of the voice coil are different from each other. This configuration of magnetization directions allow magnetic energy of neighboring magnets to be synthesized, and a magnetic flux density at the inner side of the magnetic gaps to be improved. Thus, a sound pressure level of the loudspeaker can be enhanced.
Magnetic circuit 24 configured above is coupled to a frame. The frame supports a diaphragm such that the voice coil fixed to the diaphragm is inserted into magnetic gaps 25A and 25B of magnetic circuit 24.
Herein, in order to improve the space factor, this loudspeaker has a noncircular outside shape such as an elliptic shape or a track shape or a rectangular shape. Magnetic circuit 24 also has a noncircular outside shape such as an elliptic shape or a track shape or a rectangular shape, corresponding to the outside shape of the loudspeaker.
Herein, the magnetic gaps are formed in a portion provided with magnets at outer and inner sides thereof. Furthermore, for the purpose of enhancing a sound pressure level of the loudspeaker, a magnetic circuit, in which a magnetic gap is provided in a portion provided with a magnet only at the inside by bending a bottom plate, has also been proposed.
Note here that the prior art document relating to the invention of this application includes, for example, PTL 1.